Telephone ringing system



July 15,1941; K. L. M AURER 1 2,2

TELEPHDR: RINGING SYSTBI Filed 08c. 8,1939

misc-a einlssn rm rm INVENTOR KL. AMURERv ATTORNEY Patented July 15,1941 UNITED STATES-- PATENT OFFICE TELEPHONE RINGING SYSTEM Keith L. Mau-er, Rockville Centre, N. Y., assignor to Bell Telephone Laboratories,Incorporated, New York, N; Y., a corporation of New YorkApplicationDecember 8, 1939, Serial No. 308,216

4 Claims. (Cl. 179-86) mal conditions, i. e., when the earth potentialat the stations, or the inducedpotentlal from adjacent power lines,etc., is not sumciently high, when added to the potential of the centralofiice battery during the idle or talking condition of the line, tobreak down some or all of the control gaps of the station tubes which inpractice requires about 70 volts. If such a breakdown occurs whileconversation is in progress, such discharge will cause noise in thereceivers of the parties talking. Further, if the interfering voltageoccurs in the absence of ringing potential,

it need only rise to a somewhat higher peak value to cause falseoperation of one or more of the bells connected to the-line.

An object of the present invention is to provide an arrangementemploying gas-filled tubes that will function in a satisfactory mannerand obviate noise interference and false ringing under abnormally highground and induced voltage conditions.

A feature of the present invention resides in employing three-electrodegas tubes in which the so-called main gap, i. e., the gap between theanode andeither of the other two electrodes, is non-rectifying, i. e.,will permit a current to flow in'either direction with equal facility,in connecting the control electrode and cathode to the two sides of theline in series with a current limiting high resistance, and inconnecting the anode to ground through a polarized and biased telephoneringer of a well-known type, the re sistance at each station beingconnected between the tube and the side of the line which is oppositethe side over which current must be transmitted to operate therespective ringer.

The invention will be understood from the following description andappended drawing which show a tube (Fig. 1) having the bilateral maingap characteristics previously mentioned and the method of connectingthe tube with the line and ringer to avoid noise interference and falseringing (Fig. 2).

Referring to Fig. 1, the tube l is ofthe usual of a biasing gas-filledtype containing three electrodes, two of which, 2 and 3, aresemicircular in shape and arranged in a'plane transverseof the majoraxis of the tube with thestraight edges of the electrodes close,together (of the order of 1 millimeter). The circular edges arepreferably turned downwardin a small arc to'preventexcessive blackeningof the envelope or bulb adjacent to the electrode.

The upper or outer surface of the two electrodes, .2 and 3, are coatedwith alkaline earth compounds such as oxides of barium and strontium,and thereafter activated in the usual manner.

These two electrodes constitute the so-called control gap of thetube andin practice break down at or about volts applied thereto.

The third electrode or anode 4 of the tube employed in the presentinvention, however, differs from the small untreated wire tip used intubes now in commercial service and which gives these tubes a highlyrectifying characteristic, in thatthe present anodeissimilar in shape,size and surface treatment to the other two electrodes, 2 and 3, wherebythe gap formed between either electrode 2 or 3 and the anode 4 iscapable of passing current in either direction with equal facility.

Inthe present commercial rectifying tubes the nominal main gap breakdownvoltage, i. e.,

between the tip of the wire anode and either of the other electrodes inthe absence of ionization, is of the order of 1'75 to 200 volts and thevoltage necessary to sustain a discharge there between is of the orderof '75 volts. These values could be the same and by proper designprobably exceeded in the non-rectifying tubes .of the present invention.

Now, referring to Fig. 2, C is a conventional cord'circuit having fourselective ringing keys, J. M, W and R which are adapted whenindividually operated to connect ground to either side of a connectedline L and alternating ringing current in series with a so-calledbiasing battery to the other 'side ofthe line. For example, key

J is adapted to ground the so-called ring con duetor of the it e andconnect the negative pole generator to the tip side of the line and keyR is adapted to ground the tip of the line and connect the positive poleof the biasing battery in series with the. ringing generator to the ringside.

Connected across the line at the subscribers stations J, M, W and R, inseries with current attery in series with a ringing and R break down inthe limiting resistances 5, are gas-filled tubes l of the typehereinbefore described having a main ap of bilateral conductingcharacteristics.

At stations J and M, i. e., the so-called tip parties, one of thecontrol gap electrodes 2 is connected directly to the tip conductor ofthe line and its opposing electrode 3 is connected to thering conductorin series with the current limiting resistance 5 and at stations W andR,

-i. e., the so-called ring parties, the location of the current limitingresistance is reversed. it being connected between the tip of the lineand electrode 2, while electrode 3 is connected directly to the ring.

Completing the circuit arrangement, polarized and biased telephoneringers 6, of conventional type, are connected between ground and thethird electrode or anode 4 of the tube I.

ionizationoccurs, which even in present tubes is of the order of 175 to200 volts. 2

What is claimed is:

1. In a selective signaling system, a line, a plurality of telephonestations, a source of pulsating signaling current, means for selectivelyconnecting either pole of said source to either side of the line andground and the other pole of said source to the opposite side of theline, biased telephone The operation of the circuit arrangement abovedescribed is as follows: If for example it is desired to ring the partyR, i. e., the station which responds to positive pulsatingcurrent on thering side of the line, the operator will close key R, thereby groundingthe tip conductor of the line and connecting the positive pole of thebiasing battery, in series with the ringing generator, to the "ring sideof the line.

- It is assumed that the voltage of the combined battery and ringinggenerator, during a portion of each cycle, is sufliciently high (70volts) to fire the control gap of the .tube at eachstation wherebyionization takes place. When this occurs the main gaps of the tubes atstations W to anode 4, assuming, of course, that the voltage issufiiciently high (75 volts), and current immediately flows to ground ateach of these stations through the windings of the respective ringers.The ringer at station R is biased in the usual, well-known manner torespond to pulsating current in this direction but the ringer at stationW is biased in the opposite direction and therefore does not respond.

Similarly, the ringer at station W will respond to connection ofnegative pulsating current to the ring conductor ofthe lineby theoperation of key W, but the ringer at station R, being positivelybiased, does not respond.

Due to the inclusion of the high value current limiting resistance 5between the ring side of the line and electrode 3 at stations J and M,insufll-' cient main gap current is permitted to flow to actuate theringers at these stations. If, however, key M is operated, the ring.side of the line is grounded and positive pulsating current is connectedto the tip whereupon the control gaps of. all tubes break down asbefore, causing ionization and current to flow across the main gaps atstations J and M. The ringer at station M is biased to respond topositive pulsating current and therefore the bell at this station willring but the ringer at station J is biased in the direction of electrode3' opposite direction and therefore its bell will be silent. For'thesame reason as before mentioned, the main gaps of the tubes at stationsW and R will not receive sufilcient current, due to resistance 5, tooperate the ringers at these stations.

From the standpoint of noise and false operation of the ringers duringnon-ringing intervals, due to, induced or ground potentials, aspreviously discussed, the present arrangement is an improvement over theprevious arrangement for the reason that the interfering voltage mustreach the breakdown potential of the main gap before '75 ringers at eachstation adapted to respond to and a three-element gas-filled dischargedevice comprising an anode and two other closely spaced electrodesassociated with each ringer and so connected that said closely spacedelectrodes are connected to opposite sides of the line in series withthe respective high resistances, and said anodes are connected to groundin series with the respective ringers, said discharge devices being soconstructed that a bilateral discharge path of substantially equalconducting characteristic exists between said anode and either of saidother electrodes, and said resistances are connected in such a mannerthat at stations whose ringers are desired to respond to pulsatingcurrent applied to one side of the line, the respective resistances areconnected between the tubes and the other side of the line. I

2. In a four-party selective ringing telephone system, in combination, aplurality of subscribers stations, a biased ringer, a high resistanceelement, and a gas-filled discharge device compris ing an anode and twoother closely spaced electrodes at each station, a source of pulsatingringing current for actuating said ringers, means ior selectivelyconnecting either pole of said source to either side of the line andground and the other pole to the opposite side of the line, saiddischarge devices being so constructed that a discharge between theanode and either of' said other electrodes encounters substantially thesame impedance to the passage of current in either direction, aconnection between each anode and ground including the respectiveringer, and connections at each station between the respective opposingelectrodes and opposite sides of the line, the connection to the tip ofthe line at two stations including the respective high resistanceelements and at another two stations, said resistance elements beingincluded in the connections to the ring side of the line.

3. In a four-party selective ringing telephone system employing positiveand negative pulsating currents, and a three-electrode gas tube, a highresistance and a biased ringer at each station, characterized in thisthat the impedance of the discharge path between the anode and either ofthe other two electrodes of said tubes is substantially the same tocurrent flowing therethrough in either direction, in connecting theanode of line, four biased telephone ringers and a threeelectrode gastube associated with each ringer,

essence 3 anode end either of said electrodes, two of said ringers beingconnected between their respective anodes and ground in such e manner esto respond to pulsating ringing current in one direction and the othertwo ringers co'nnected'in a similar manner to respond to current in theopposite direction, a. connection between the cold 10 connected to theother sie electrodes of each tube and opposite sides of the line, meansfor selectively grounding either side i of the line and connectingpulsating ringing curent of either polarity to the other side, and ahigh resistance associated with each tube and connected between one ofits respective cold electrodes end the side of the line which will begrounded when ringing current of the proper direction to operate thecorresponding ringer is URER.

